The institute used a database of brain wave patterns representing thoughts about various objects

A Japanese research institute says it can tell what people are dreaming about by analyzing their brain waves.

The lab at the Advanced Telecommunications Research Institute International, or ATR, said Friday that its method matches the subject of dreams to one of about 20 general categories, with roughly 70 percent accuracy. The lab created software that can identify brain wave patterns corresponding to general concepts such as "book," "food," or "female."

ATR, whose investors include Japan telecommunications giant NTT and wireless operator KDDI, said it aims to improve the field of brain-machine interfaces with the research. ATR's Brain Information Communication Research Lab, which carried out the experiments, said the results may also be applied to subjects that are awake but have trouble expressing themselves, such as people who suffer from hallucinations or are mentally ill.

The lab experimented on three test subjects, hooking them up to an EEG (electroencephalogram) and having them sleep inside an MRI machine to measure their brain waves. When an identifiable pattern emerged, the subjects were immediately awakened and asked what they were dreaming about, a process that was repeated about 200 times for each person, creating a database of dream subjects and corresponding brain wave patterns.

The results were grouped into general categories, and the subjects were then shown images that corresponded to each category, with their resulting brain waves patterns also recorded. As brain activity when dreaming about objects or actually viewing them is thought to be similar, this added more entries to the database created during the sleeping tests.

The lab said it found that databases created in this way could be used to accurately determine what the subjects were dreaming about. The results were most accurate when used on dreams that the subjects experienced less than 15 seconds before they were awakened. As more time elapsed, the subjects appeared to forget what they had been dreaming about.

The lab said it is unsure whether similar results can be obtained for identifying patterns or colors, as opposed to general concepts and ideas.

ATR is based in Kyoto Prefucture in central Japan. In addition to working with corporations, it also works with government agencies on projects ranging from robotics to wireless technologies.